Ashshamsu walqamaru bihusban (surah Rahman: 5)

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(55:5) The sun and the moon follow a reckoning, *4

Ashshamsu walqamaru bihusbaan

*4) That is, "It is a powerful law and unalterable system that binds the great planets together. Man is able to calculate and measure time, days, dates, and crops and seasons only because no change takes place in the rule that Has been laid down for the rising and setting of the sun and of its passing through different stages. The innumerable creatures found on the earth are staying alive only because the sun and the moon have been accurately and precisely placed at particular distances from the earth and any increase or decrease in this distance is made in the right measure, in a particular order; otherwise if their distance from the earth increased or decreased haphazardly, no one, could possibly survive here. Likewise, the perfect relationship and harmony that has been established between the movements of the moon round the earth and the sun, has made the moon a universal calendar, which announces the lunar date every night to the whole world with perfect regularity.